I've used lots of time to make several dungeons and dragons GPTs that do everything from creating worlds and multiverses, creating adventures, creating characters and being the DM in a 1 on 1 text based D&D game.
I also made a D&D judge GPT that would judge any given difficulty in D&D or between players and DM.
In addition to advice on what to do, it also creates an appropriate punishment and boon that can be used ingame.
It's abit sad though, because AI isn't accepted among the D&D community.
But I would think AI would benefit D&D a lot and make the game more accessible.